Hello,
I am working on building a dirt circle race car from an 86 cavi. I have the 2.0 engine and a manual trans in it. I modified the intake and am using a holly/weber carb on it. I do not have the ecm for it nor do I want it. I have the distributer ignition and was wondering how I can go about getting spark using the dist and coil with no ecm. Our cars typically see muddy conditions and a lot of abuse so I want to make it simple with as little electronics as humanly possible. If any one has any suggestions on how to do this I would be rather great full!! I was able to achieve this with our last race car (VW rabbit) by using the dist, coil and ignition module and no ecm, but am unsure how to approach this with the cavi. Thanks very much for your help!!!
What you want should be easy to do. The distributor will generate spark during cranking. At this point the ecm is not involved in the timing. After the engine hits about 600 RPM the ecm sends 5V on the Bypass line and the ignition module begins receiving timing signals from the ecm. If 5V is never applied to Bypass, the distributor keeps generating spark without the ecm. So the short answer is install the distributor and hook up any wires which weren't connected to the computer, should be a 4 wire connector hanging out of the distributor. IIRC the coil's not in the cap on this engine, so there's a fat pink power wire to the coil and a 2 wire connector between the coil and distributor with pink and white wires. Hook these up and you're good to go.
The ignition module will provide a bunch of advance usually around 2500 rpm. I've seen advance increase as much as 10 degrees in about a 1000 RPM change from some of the modules. It's almost like flipping a switch. Set your timing at about 3000 RPM for the maximum advance you want, then measure the timing at idle and you'll always know where to set timing in the future.
Things change if you're running an MSD. You'll need to work out how you want to trigger the ignition.
HTH
-->Slow
im not sure what early 1.8/2.0l ohv motors ran, but i do not beleive they were computer controlled. this may be an option, as it may be a typical hei ignition and have mechanical weights and points. aside from that, the 7 or 8 pin hei will run without an ecm inputs, however it may not be the ideal timing curve.
Unfortunately they were all computer controlled. The first 1.8 in '82 was carburetted and had a CCC system which would pulse mixture control solenoids in response to lean / rich signal from the O2. Timing was based on MAP engine temp. '83 went to TBI which was used until the new engine design was released in '87.
I do not know of a weight and spring distributor which will fit in this engine. Maybe an older 2.5 dizzy with the correct lower gear? Maybe a Chevette 1.8 distributor?
-->Slow
hmmm well i guess the best bet is to run the distributor without the ecm and set the total timing at 3000rpm and lock it down. the only thing i dont like is the 7/8 pin hei modules are not known for reliability, one time they work, next time they dont. for this reason id try to convert and put points in it, or a pertronix module if at all possible.
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for this reason id try to convert and put points in it, or a pertronix module if at all possible.
Well, he could use the pickup coil to trigger an MSD but then he'd have to use an additional timing computer to generate an advance curve.
Doesn't MSD make a 7 pin HEI module? I'm sure I've seen aftermarket replacements.
-->Slow
thing is being a race car, you dont need an advance curve. typicaly you are at your total timing above 3000rpm, and in many cases you try and have total timing in sooner. in a race car were fuel economy isnt a concern, locking the timing in perfectly fine.
